Phenotypic markers and history of the introduction of white-lipped snail Cepaea hortensis (Gastropoda, Helicidae) in western regions of Ukraine

Abstract

The dependence of the introduction history of Cepaea hortensis in the western regions of Ukraine and the phenotypic variability of this species, concerning the shell and body colouration, is analysed. In areas inhabited by descendants of the primary introduction (most likely, the second half of the 20th century, but not later than the 1970s) no more than three main variants of shell colouration are observed: yellow or white unbanded, white banded. There is also no variability in the body colouration; all snails have a light body, without gray or reddish pigment. The most characteristic feature of such colonies, which can serve as a phenotypic marker, is the presence of dark spiral bands only on white shells. An analysis of photographs from different parts of the present range of C. hortensis, significantly expanded due to anthropochory, made it possible to find out that shells with a white ground colour and especially white banded shells are found in different countries of Europe and North America. However, white is not the only colouration variant of the banded shells there. Conversely, yellow banded shells are one of the typical colouration variants in different parts of the range of C. hortensis. Recently, at some sites of Western Ukraine, colonies of C. hortensis with a different phenotypic composition have begun to be found, formed as a result of repeated introductions of this species, which pass through various garden centres. Such colonies are characterized by the presence of yellow banded and sometimes also pink shells as well as by a more or less pronounced variability in body colouration. The most interesting is the presence at some sites of Lviv and its environs of a rare hereditary trait that is only locally found in the natural range of C. hortensis, namely, the dark lip in some adults. At sites with the presence of such a feature, all pink and single yellow shells have a dark lip. We found out that the spreading of carriers of this trait occurs through the garden centre "Club of Plants", located near Lviv (Pidbirtsi). At the same time, at some sites of Lviv and its environs, where pink shells were also found, all of them had a light lip, characteristic of C. hortensis. This indicates that repeated introductions of C. hortensis, even within the same Lviv, not only pass-through different garden centres, but also have different origins.